Disk brake equipped with a mechanical actuating device

ABSTRACT

A disk brake having at least one piston (14) which slides in a caliper (12), the caliper (12) sliding over a stationary support. The piston (14) being actuateable by a mechanical subassembly (22) having substantially first (24) and second (26) parallel plates. The first plate (24) being driven in rotation by a lever (32) about an axis (X--X&#39;) perpendicular to its surface. The second plate (26) being held in a stationary position with respect to rotation and secured to piston (14). A face on at least one of the first (24) and second (26) plates has a groove formed therein for receiving balls (28) to convert rotational movement of the first plate (24) into axial transulational movement of the second plate (26). The lever (32) has a first part (34) fastened onto an end (36) of a sheath of an actuating cable (38). The sheath (40) bearing on an end stop member (42) which is held stationary with respect to the caliper (12). The sheath (40) has an end stop member (42) which is formed on a brace member (44). The stop member (42) angular position about the axis (X--X&#39;) with respect to the lever (32) is determined by the angular position of the lever (32) with respect to the caliper (12).

BACKGROUND OF THE INVENTION

The present invention relates to the field of disk brakes in general, ofthe type of those used to provide braking on motor vehicles.

Such disk brakes in the known fashion include at least one pistonsliding in a caliper itself sliding over a stationary support. Thepiston may be actuated hydraulically for service brake operation, andmechanically for emergency brake or parking brake operation.

Mechanical actuation may, for example, be provided by a mechanicalsubassembly comprising two substantially parallel plates, a first platebeing able to be driven in rotation by an operating lever about an axisperpendicular to its surface, a second plate being stationary in termsof rotation and secured to the piston, the face of at least one of theplates being formed with inclined grooves taking balls for convertingthe rotational movement of the first plate into an axial translationalmovement of the second plate, the operating lever being formed with apart for fastening onto the end of a sheathed actuating cable, thesheath of the cable bearing on a sheath end stop which is stationarywith respect to the caliper.

Disk brakes equipped with such mechanical actuators are well known inthe art, for example from document FR-A-2,638,214. They do, however,have some drawbacks. In fact, series production requires the provisionof manufacturing tolerances for the various elements making up the diskbrake and the plate-type mechanical actuator.

As a result, during final assembly of the disk brake, the mechanicalactuating lever is, at rest, in an angular position which can vary frombrake to brake, with respect to the stationary sheath limit stop, acrossa not insignificant range of values. For example, variations of plus orminus 10 degrees have been observed.

It therefore follows that when the disk brake is installed on thevehicle, the maximum angular excursion of the lever between its positionof rest and its extreme position closest to the stationary limit stopitself varies from brake to brake and that in some extreme cases thismaximum angular excursion is insufficient for satisfactory mechanicalactuation of the disk brake.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a disk brakewith a plate-type mechanical actuation device of the type recalledhereinabove, in which the distance between the sheath limit stop, whichis stationary with respect to the caliper, and the part for fasteningonto the end of the sheathed actuating cable is constant from brake tobrake in series production, and regardless of the initial position ofthe lever, bearing in mind the manufacturing tolerances, by providingmeans which are simple to employ and inexpensive so as to be compatiblewith such series production.

To this end, according to the invention, the sheath limit stop is formedon a bracing piece of which the angular position with respect to thelever is determined by the angular position at rest of the lever withrespect to the caliper.

As a result, the travel of the actuating cable, and consequently theangular excursion of the operating lever, can be constant from brake tobrake and set to the optimum value for the disk brake thus equipped.

According to an advantageous embodiment, the bracing piece includes anarm formed with a tab extending perpendicularly to the arm and forming afirst limit stop against which the lever comes to bear in a firstposition.

For preference, the bracing piece is formed with an oblong slotextending substantially along an arc of a circle centered on the axis ofrotation of the lever, and the oblong slot of the bracing piece haspassing through it the shank of a screw secured to the caliper, so thatthe bracing piece can be immobilized in terms of rotation by a nutscrewed onto the screw shank.

Other objects, features and advantages of the present invention willemerge more clearly from the description which follows of one embodimentgiven by way of non-limiting explanation, with reference to the appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section through a disk brake equipped with a mechanicalactuating device;

FIG. 2 is an end-on view of the mechanical actuating device according tothe present invention, in the position of rest;

FIG. 3 is a view similar to that of FIG. 2, in an extreme actuatingposition;

FIG. 4 is a view on IV of FIG. 2;

FIG. 5 is a view on V of FIG. 3;

FIG. 6 is a view similar to that of FIG. 2, of an alternativeembodiment, and

FIG. 7 is a section on VII--VII of FIG. 6.

DETAILED DESCRIPTION OF THE DRAWINGS

Recognizable from FIG. 1 is a disk brake comprising a body 10 acting asa housing for the system for actuating the disk brake, the body 10 beingsecured to a caliper 12 slidably mounted on a stationary part (notrepresented) of the vehicle, such as the stub axle holder, in order tobrake a rotating disk 11 secured to a wheel (not represented) of thevehicle.

Actuation of the disk brake may be hydraulic, via a piston 14 mounted sothat it can slide in a leaktight fashion in a bore 15 of axis X--X' madein the body 10, the movement of this piston being brought about by thehydraulic pressure in a chamber 16 situated behind the piston 14, andconnected by a pipe 18 to a pressure source such as a master cylinder(not represented).

The piston 14 thus presses a friction lining 20a against one face of therotating disk 11, whilst by reaction the caliper 12 presses anotherfriction lining 20b against the other face of the rotating disk 11.

Actuation of the disk brake may equally well be mechanical, using aplate-type actuator denoted overall by the reference 22. The actuator 22includes two plates, an inner plate 24 and an outer plate 26, betweenwhich balls 28 are located.

The plate 24 is immobilized in terms of rotation, for example by a peg25 secured to the body 10, for example inserted via the pipe 18. It isfree in terms of translation inside the body 10 and it is secured to thepiston 14 via a device denoted overall by the reference 30 and intendedautomatically to take up any play resulting from the progressive wear ofthe friction linings 20a and 20b.

The plate 26 is free in terms of rotation about the axis X--X', and itincludes a pivot 26a projecting out of the body 10 and secured to anactuating lever 32 extending outside of the body 10. The plate 26 bears,via a ball bearing or roller bearing device 33, against a surface 35perpendicular to the axis X--X'.

At least one of the opposing faces of the plates 24 and 26 is formedwith curved grooves about the axis X--X', and the bottom of which isinclined with respect to a plane perpendicular to the axis X--X', sothat the rotation of the plate 26, brought about by the lever 32, isconverted into a translation of the plate 24, and correspondingly into amovement of the piston 14 toward the disk 11.

The lever 32 is actuated in the conventional way by a sheathed cable. Ascan clearly be seen in FIGS. 2 to 5, the end of the lever 32 is bentinto the shape of a U in order to form a groove 34 for the fastening ofa ferrule 36 crimped onto the end of an operating cable 38.

The cable 38 constitutes the core of a sheathed cable, the sheath 40 ofthis cable coming into abutment on a sheath limit stop 42 formed on abracing piece 44. In the example represented, the bracing piece 44 isfitted in between the lever 32 and the rear part 46 (FIG. 1) of thecaliper 12. This part 46 of the caliper is formed with a cylindricalboss 48, centered on the axis X--X', about which boss the bracing piece44 can slide, pivoting about the axis X--X' by virtue of a circularcutout 50 of corresponding diameter.

The bracing piece 44 includes an arm 52 extending, for example, aroundthe circular cutout 50, and at the end of which is formed a tab 54extending in a direction substantially perpendicular to that of the arm52 and forming a first limit stop for the lever 32 when the latter is inthe position of rest represented in FIGS. 2 and 4.

The bracing piece 44 includes a second limit stop 55 for the lever 32when the latter is in the extreme actuating position, represented inFIGS. 3 and 5.

Finally, the bracing piece 44 is formed with an oblong slot 56 extendingsubstantially along an arc of a circle 58, concentric with the circularcutout 50. The circular arc 58 is therefore centered on the axis X--X'of rotation of the lever 32 when the bracing piece is in place on thecaliper 12. The oblong slot 56 serves to immobilize the bracing piece 44on the caliper 12, for example by means of a screw 60 passing throughthis opening and screwed into a tapped bore made in the rear part 46 ofthe caliper 12.

From the foregoing description, it will have been understood how theinvention is put to use. Having completed the assembly of the diskbrake, when all the components have been installed in the bore 15, thebracing piece 44 is put in place around the cylindrical boss 48, and thelever 32 is secured to the pivot 26a, for example by force-fitting.

Advantageously, the pivot 26a may have a non-circular shape, in theshape of a star as has been represented in FIGS. 2 and 3, or in theshape of a polygon or a splined shape, interacting with an opening ofcorresponding shape in the lever 32, in order to ensure that the plate26 is driven by the lever 32 in rotation without play.

It was seen above that, after this final assembly, owing to themanufacturing tolerances, the angular position of the lever 32 withrespect to the caliper 12 lies within a relatively broad range ofvalues. All that then need be done is to rotate the bracing piece which,at this time is free to rotate, about the boss 48 in order to bring thetab 54 into abutment on the lever 32, in the position illustrated inFIGS. 2 and 4, then to immobilize the bracing piece 44 in this positionon the caliper 12 by tightening the screw 60.

The disk brake is then set as soon as its manufacture is completed, andit is ready to be installed on a vehicle without further manipulation.Indeed, as the position of the bracing piece 44 has been defined by theposition at rest of the lever 32, it follows that the position of thesheath limit stop 42 is then at a distance from the fastening groove 34which depends merely on the geometry of the bracing piece 44, and thatthis distance is therefore identical for all the disk brakes thusmanufactured.

It can therefore been seen that the angular travel of the lever 32, orthe linear travel of the cable 38, between the position of restillustrated in FIG. 2 and the extreme position illustrated in FIG. 3 inwhich the lever 32 is bearing on the limit stop 55, is independent ofthe initial position of the lever 32, and consequently of themanufacturing tolerances.

When the disk brake is installed on a vehicle in the course of assembly,after the caliper 12 has been fitted to the stub axle holder, theoperating cable 38 can be connected to the disk brake. In order to dothis, the sheath 40 is brought to bear on the sheath limit stop 42, andthe cable 38 is slipped into the groove 34 in order to fasten theferrule 36 therein.

With the disk brake having been set up as has just been explained, onecan be sure that the ferrule 36 is at the desired distance from thesheath limit stop 42, and that it can accomplish the entire actuationtravel intended for such a disk brake, between the position of rest ofFIGS. 2 and 4 and the extreme actuation position of FIGS. 3 and 5, inwhich the lever 32 is bearing on the limit stop 55. No additionalsetting is therefore required on the vehicle assembly line.

The maximum angular excursion of the lever 32 is thus determined solelyby the angular distance between the two limit stops 54 and 55, bothformed on the bracing piece 44. Likewise, the angular distance at restbetween the ferrule 36 and the end of the sheath 40 of the cable isdetermined solely by the geometry of the bracing piece 44 when it isbearing, via the limit stop 54, against the lever 32.

The bracing piece allowing these operations may easily be produced bypressing a metal sheet, and it therefore does not significantly increasethe cost price of the disk brake thus obtained. Furthermore, it bearsthe limit stops 42, 54 and 55 and thus constitutes a limit stop piecewhich can be manufactured in a single operation. The angular distancesbetween these various limit stops can therefore be respected with quitegood accuracy.

It is thus clear that the maximum excursion of the lever 32 will beensured in all cases, regardless of the angular position at rest of thelever 32. The setting-up of the mechanical actuating device as providedfor by the invention has no influence on this maximum excursion. It hasthe sole effect of varying, slightly, the slack in the cable between thesheath limit stop 42 and, for example, the handbrake lever (notrepresented) situated in the passenger compartment of the vehicle.

It can therefore clearly be seen that the setting means provided by theinvention are particularly simple to use because all that required,during manufacture of the disk brake, is to bring two components intoabutment one on the other, and to tighten a screw, then to install thisbrake on a vehicle without further setting.

Another significant advantage afforded by the invention is that it ispossible very easily to get back to this initial setting position, evenafter the screw 60 has been accidentally removed, for example by someonenot familiar with this type of brake.

As can be seen in FIGS. 6 and 7, the oblong slot 56 is formed in asecond arm 62 of the bracing piece 44, accommodated in a curved groove64 extending along an arc of a circle centered on the axis X--X'. Thegroove 64 is formed between the cylindrical boss 48 and a part 66 of thebody 10 projecting axially toward the rear of the caliper 12.

The tapped bore 61 designed to interact with the screw 60 is made in thebottom of this groove, substantially in the middle of the circular arcwhich it forms. The groove 64 thus participates in guiding the bracingpiece 44 when it is rotated about the cylindrical boss 48 in order toset it, as has been explained above.

Furthermore, a concave radial depression 68 is formed in the wall of thegroove 64 formed by the cylindrical boss 48, the center of thisdepression 68 being situated substantially on a radius joining the axisX--X' to the axis of the tapped bore 61.

Likewise, a concave radial depression 70 is formed in the wall of thegroove 64 formed by the projecting part 66 of the caliper 12, the centerof this depression 70 being situated substantially on a radius joiningthe axis X--X' to the axis of the tapped bore 61, so that the twodepressions 68 and 70 face each other on each side of the axis of thetapped hole 61.

Finally, the screw 60 includes, between its operating head 72 and itsthreaded shank 74, an intermediate part 76 of axial length substantiallyequal to the thickness of the bracing piece 44, and the cross-section ofwhich adopts a cam shape, the largest diameter of which is greater thanthe initial width of the oblong slot 56.

When the brake is being set in the way which has already been explained,once the tab 54 is bearing on the lever 32, the initial effect oftightening the screw 60 in the bore 61 is to hold it radially in thecaliper 12.

Then, as the screw 60 is tightened further, the intermediate part 76 isbrought into the vicinity of the edge of the oblong slot 56. Thecam-shaped cross-section of the intermediate part 76 then deforms thewalls of the slot 56, which deformation is passed on to the material ofthe arm 62, the depress then expand into the depressions 68 and 70,therein forming bumps 68' and 70' respectively. The bracing piece 44 isthus in its optimum position as defined above.

In contrast, if the screw 60 is taken out following an incorrectoperation, the bracing piece 44 is no longer held and can then escape.It will then be very easy to put it back in place, and what is more, toput it back in place in its initial and optimum setting position. Infact, it will have been understood that the only possible angularposition for the bracing piece 44 on the caliper 12 is the one in whichthe bumps 68' and 70' are put back in place in the depressions 68 and70.

All that will then be required will be to put the bracing piece 44 backinto this position, then to retighten the screw 60, or even some otherscrew which does not have the intermediate cam-shaped part 76, in orderto regain the disk brake with its optimum initial setting.

Of course, the invention is not limited to the embodiments which havebeen described, but can in contrast receive numerous modifications whichwill be obvious to the expert, without departing from the scope of theappended claims. Thus, for example, omitting the projecting part 66 ofthe caliper, that is to say omitting one of the radial walls of thegroove 64 may be envisaged. In this case, the angular position of thebracing piece 44 corresponding to its initial setting will be identifiedby just one bump 68' interacting with the single depression 68 formed onthe cylindrical boss 48.

We claim:
 1. A disk brake including at least one piston sliding in acaliper, said caliper sliding over a stationary support, said pistonbeing actuateable by a mechanical subassembly comprising first andsecond substantially parallel plates, said first plate being able to bedriven in rotation by a lever about an axis perpendicular to itssurface, said second plate being stationary in terms of rotation andsecured to said piston, at least one of said first and second plateshaving a face formed with inclined grooves retaining balls forconverting rotational movement of said first plate into an axialtranslational movement in said second plate, said lever having a partconnected onto an end of a sheath for an actuating cable, said sheath ofthe cable bearing on a sheath end stop piece held in a stationaryposition with respect to said caliper, characterized in that said sheathend stop piece is formed on a bracing member, said bracing member beinglocated in a first angular position about an axis with respect to saidlever, said first angular position being determined by a second angularposition of the lever with respect to the caliper, said bracing memberincluding an arm formed with a tab extending perpendicularly to said armand forming a first limit stop against which said lever comes to bear ina first position, said bracing member being formed with an oblong slot,the long axis of said oblong slot extending substantially in an arc of acircle centered on said axis of rotation of said lever, said bracingmember being immobilized in terms of rotation with respect to saidcaliper by means of a screw passing through the oblong slot of thebracing member and interacting with a tapped bore made in said caliper.2. The disk brake according to claim 1, characterized in that saidbracing member is formed with a second limit stop against which saidlever comes to bear in a second position.
 3. The disk brake according toclaim 2, characterized in that a first position of the lever correspondsto its position of rest, and in that a second position of the levercorresponds to its position of maximum excursion.
 4. The disk brakeaccording to claim 3, characterized in that at least one concave radialdepression is formed in one of the radial walls of said curved groove.5. The disk brake according to claim 1, characterized in that saidoblong slot is formed in a second arm of the bracing member, said secondarm being accommodated in a curved groove extending along an arc of asecond circle centered on the axis of rotation of said lever, saidgroove being formed between a cylindrical boss and a projecting part ofsaid caliper.
 6. The disk brake according to claims 5, characterized inthat said curved groove includes a concave radial depression in a wallformed by said cylindrical boss and a concave radial depression in thewall formed by said projecting part, the centers of the concave radialdepressions being aligned on a radius joining the axis of rotation ofsaid lever and the axis of said tapped bore interacting with said screw.7. The disk brake according to claim 6, characterized in that said screwincludes, an intermediate part located between an operating head and athreaded shank, said intermediate part having a cross-section of whichadopts a cam shape of which the largest diameter is greater than theinitial width of said oblong slot.